Recent studies have highlighted the dynamic role of the adventitia in the genesis of atherosclerosis,¹ atherothrombotic events² and restenosis after balloon angioplasty.³

Intravascular ultrasound (IVUS) provides a unique means of studying atherosclerosis in vivo, but the lack of any acoustic interface behind the adventitia notoriously prevents analysis of the adventitia. Careful analysis of IVUS images, however, often finds slight pericardial detachments just to the rear of the artery being explored. This situation creates a new anechogenic acoustic medium at the external edge of the adventitia, setting up a new acoustic interface, thus clearly identifying the adventitial tunica (fig 1).

We first conducted an ex vivo study to test this hypothesis and validate the precision of the adventitia measurements. The relevance of such data in humans in vivo was then assessed by IVUS studies of the left anterior descending …